The principal investigator has had a long-term commitment to a career in academic medicine. Following the completion of a M.D.-Ph.D. degree at the University of Chicago, he is now completing training in an academic pathology residency at the University of Pennsylvania, with an emphasis in gynecologic pathology. The CIA will allow the candidate to bridge his research and clinical training and develop into an independent biomedical investigator. Research: The principal investigator proposes to study the regulation of steroidogenesis in the human trophoblast. He has purified a population of cells from human term placentae which, by structural features and steroidogenic activity, are trophoblasts. Immunochemical staining for hCG, hPL, low molecular weight keratin, vimentin and alpha-1 anti-chymotrypsin indicated that these cells are cytotrophoblasts. Preliminary findings suggest that they transform into synctialtrophoblasts in short-term culture with a concomitant 8-fold increase in progesterone synthesis and 3-9-fold increase in hCG production. The aims of the proposed research are to determine 1) whether the syncytial elements form by cell fusion or endomitosis; 2) the temporal changes in steroidogenesis as syncytia form; and 3) define the factors (hormones or paracrines) which regulate steroidogenesis and syncytium formation in culture. Environment: The principal investigator will perform the proposed research under the guidance of Dr. Jerome Strauss, Director of the Division of Reproductive Biology (DRB), in the Department of Obstetrics and Gynecology and a member of the Department of Pathology and Laboratory Medicine. The Division of Reproductive Biology includes eight full time investigators whose research focuses on molecular and cellular aspects of reproduction. These investigators can be called upon for consultation. In addition to the facilities of the DRB, the facilities of the Department of Pathology and Laboratory Medicine, including the electron microscopy and immunocytochemical laboratories, will be available for this study.